Curtis L. Fincher

Thermal modeling of continuous‐wave end‐pumped solid‐state lasers

In order to estimate deleterious effects caused by heating in continuous‐wave end‐pumped solid‐state lasers, the heat equation has been solved for an axially heated cylinder with a thermally conductive boundary at the periphery. Steady‐state thermal profiles are developed using both a full numerical solution and an analytic approximation which assumes only radial heat flow. The analytic solution, which is in good agreement with the numerical solution, is utilized to obtain an expression for the thermal focusing due to temperature‐induced refractive index changes. For Nd:YAG, 1 W of pump power deposited as heat is predicted to cause a thermal focusing length comparable to the cavity length of a typical diode end‐pumped laser.

Highly efficient Nd:YVO4 diode‐laser end‐pumped laser

We report on the first diode‐laser (nominal 200‐mW 10‐stripe laser diode) end‐pump lasing of Nd:YVO4. The lowest threshold (30 mW) and highest output power (120 mW) were observed from the Nd:YVO4 laser as compared to a similar Nd:YAG laser. Over 50% optical slope efficiency was obtained, the highest yet reported for diode pumping. This device performed at a 10% overall efficiency. Measurements over a 21‐nm range show the advantages of the Nd:YVO4 pump absorption band.

Stimulated‐emission cross section at 1064 and 1342 nm in Nd : YVO4

The stimulated‐emission cross sections at 1064 (4F3/2→4I11/2) and 1342 nm (4F3/2→4I13/2) in Nb : YVO4 were determined by measurement of laser thresholds as a function of output mirror reflectivity. Small samples of Nd : YVO4 and Nd : YAG were end pumped at room temperature with a cw 514.5‐nm argon ion laser in an almost identical geometrical arrangement which permitted comparative values to be obtained. Assuming that the pumping quantum efficiency of Nd : YVO is similar to that of Nd : YAG, the stimulated‐emission cross sections obtained for the 1064‐ and 1342‐nm transitions were respectively 12×10−19 and 6.0×10−19 cm2.

Continuous‐wave operation of Nd : YVO4 at 1.06 and 1.34 μ

Continuous‐wave plane‐polarized outputs of 1 W at 1.06 μ and 0.35 W at 1.34 μ were obtained by end pumping small samples of Nd : YVO4 with an argon‐ion laser. Slope efficiencies and material losses were determined. At 1.06 and 1.34 μ, Nd : YVO4 lasers can substantially outperform Nd : YAG lasers. Self‐Q‐switched operation of Nd : YVO4 at both wavelengths was obtained by resonator misalignment.

Laser emission cross section of Nd:YAG at 1064 nm

The stimulated emission cross section of Nd:YAG (yttrium aluminum garnet) (4F3/2→4I11/2) was compared to the known cross section of Nd:ED‐2 glass at 1060 nm. Small samples of Nd:YAG and ED‐2 glass were end pumped with a chopped cw 514.5‐nm argon‐ion laser in an identical geometrical arrangement. The stimulated emission cross section obtained for Nd:YAG at 1064 nm was found to be 7.6 ×10−19 cm.

Fluorescence determination of atmospheric NO2

The concentrations of nitrogen dioxide (NO2) in the atmosphere have been determined in real time and with a sensitivity of one part per billion. Laser excitation of NO2 was at 4416 and 4880 Å and fluorescence was monitored at 0.7 to 0.8 μm. Results obtained on typical smoggy days in Los Angeles are presented.

Atmospheric NO 2 determination by 442-nm laser induced fluorescence

An atmospheric monitor with a detectability of 0.6 ppbv, utilizing a compact He-Cd laser at 442 nm for excitation of the NO(2) molecules is described. Photon-counting techniques were employed to detect the NO(2) fluorescence transmitted through a bandpass liquid solution filter that did not fluoresce upon absorption of scattered laser light. Operational characteristics of the instrument are described. Results obtained in ambient air monitoring are presented.

THE RUBY LASER: PUMPED BY A PULSED ARGON ION LASER

A ruby laser with a pulsed argon ion laser as a pump was constructed and operated at 77° and 300°K. Threshold for oscillation was ∼13 mJ. A unique type of Q‐switched operation was observed that produced pulses of ∼15 nsec at 300°K and ∼6 nsec at 77°K.

Stimulated emission cross sections of Nd:YVO4 and Nd:La2Be2O5 (BeL)

The stimulated emission cross sections σ of the 4F3/2→4I11/2 transitions have been measured for a‐axis Nd:YVO4 (1064.1 nm, σ = 19.0×10−19 cm2), x‐axis Nd:BeL (1079.2 nm, σ = 1.54×10−19 cm2), and y‐axis Nd:BeL (1070.1 nm, σ = 2.31×10−19 cm2).

CONTINUOUS‐WAVE NONSPIKING SINGLE‐MODE RUBY LASERS

Continuous‐wave nonspiking single‐mode operation of ruby lasers cooled to 77 and 4.2 °K was obtained by end pumping the ruby with the 5145 A output of a cw argon ion laser. Measurements of the output of the cw ruby laser showed single mode (TEM00q) operation with a full spectral width of approximately 35 kHz.